The autonomous sub-hunter hit 27 knots, or about 31 mph. It certainly isn't the fastest ship in the Navy, but the ACTUV can travel thousands of miles and operate for months on end in the open sea without a single crew member on board. Designed to locate and trail nuclear-powered submarines autonomously—which only have a top speed of about 25 knots underwater—the ACTUV is a completely new class of Navy vessel, and so far it looks like it's getting its sea-legs just fine.

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